This pushing technique is only effective for a short dive into ground effect and if you are flying a draggy type of aircraft the effect will be very slight. If you have to maintain the extra speed in the dive you've started too high and won't get the full potential benefit.
You also make use of the fact that in the ballistic bit of the aircraft may be flying flying slower than the 1g stall but, having a lower angle of attack, you don't stall.
If you make it over the obstacle, you then have to hope that you still have sufficient energy to flare, so you can see how 'last ditch' the technique is.
It is fun though!